1. Field Of The Invention
This invention relates to lubricated packing assemblies for reciprocating pumps, and more particularly, to a pump packing assembly wherein discharge fluid blowby across the packing is vented to the atmosphere by a venting zone which is separated from a lubrication portion of the assembly.
2. Description Of The Prior Art
Reciprocating pumps require packing to seal along the pump plunger or piston rod to prevent or at least minimize leakage of the fluid being pumped. Frequently, a lubricant is provided to the packing to lubricate between the packing and the plunger or piston rod. Of course, this is done to increase packing life.
A problem occurs where the pumped fluid is incompatible with the lubricant and/or where the discharge pressure of the pump exceeds the lubrication pressure which is frequently the case. Leakage of the pumped fluid into the lubricant can dilute the lubricant, thereby reducing its effectiveness. Also, the pressure from the pumped fluid can stop the flow of lubricant altogether so that no film of lubricant is provided between the packing and the plunger or piston rod.
One solution is to separate the portion of the packing assembly which seals the pumped fluid from the portion which provides lubrication to the plunger or piston rod. In this way, any leakage of the pumped fluid may be drained before it contaminates the lubricant or pressurizes any lubrication annulus. That is this separation would prevent pumped fluid pressure from shutting off lubrication.
One apparatus which generally shows these features is the stuffing box disclosed in U.S. Pat. No. 3,054,619 to Pierotti. In this device, packing is used to seal on a pump plunger, and a collection ring is disposed adjacent to the packing. The collection ring has drainage openings therein to avoid splashing of fluid out of the top of the stuffing box. Spaced sealing rings are positioned above the collection ring, and lubrication is provided through an opening between the sealing rings.
A problem with the apparatus of Pierotti is that it requires a relatively large number of parts, including the collection ring and other components to hold the packing and sealing rings in place. In the present invention, a single-piece seal carrier or gland is provided which hods lubrication seals and includes a lubrication passage between the seals and a generally longitudinally extending drain or vent passage which is not in communication with the lubrication passage.
The apparatus of Pierotti also does not provide any means to directly drain leakage around the outside of the packing. The present invention provides a vent zone for both the inside and outside of the packing which is in communication with the vent passage.